Add demux to mFrontendTests am: 86aa7010fd am: 6afaf8d190 am: 123934b067 am: 71be20f910 am: d3763ef9fc

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/2886926

Change-Id: I750e3ad38e378c55a307d1b56486b1c9f8da21a1
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>